The present invention relates to monochrome and color image forming apparatus applicable as, for example, a printer, a copying machine, a facsimile, or the like, and to a transfer belt unit, a cleaning device, and a cleaner unit, which are used for the image forming apparatus.
A conventional image forming apparatus, in particular, an image forming apparatus having a cleaning mechanism for removing toner remaining on a transfer belt is disclosed, for example, in JP 9-80934 A.
The image forming apparatus disclosed in the above-mentioned publication includes a charging member for charging waste toner remaining on the transfer belt after secondary transfer, and a collecting member for collecting the waste toner charged by the application of voltage. The apparatus is designed so that the charge of the waste toner on the transfer belt is equalized by applying a voltage to the charging member, and then the waste toner with the equalized charge is collected by the collecting member to which the voltage having a polarity opposite to the charge is applied.
Furthermore, a configuration using a cleaner roller is known as another conventional cleaning device having a cleaner for removing waste toner on the intermediate transfer belt or transfer belt. In this configuration, the voltage having a polarity opposite to the charging polarity of toner is applied to the cleaner, whereby the toner on the belt is removed. For example, JP 6-161288 A discloses a configuration using a metal roller as the cleaner roller.
The following is an explanation of this configuration with reference to FIG. 12. As shown in FIG. 12, a negatively charged toner image formed on a photosensitive member 201 is transferred onto a recording paper that is conveyed by the rotation of the transfer belt 202. The transfer belt 202 is rotated in the arrow direction in FIG. 12 and conveys the recording paper supporting a toner image to a winding portion at the supporting axis 203. The recording paper supporting a toner image is peeled off from the transfer belt 202 at the winding portion of the supporting axis 203 due to the stiffness of the recording paper, and then is conveyed to a fixing device (not shown) for further processing.
In this image forming process, besides the normal toner image, the toner of a residual image of a previous page, or toner fogging onto a region that is not in contact with the previous or subsequent recording pages is attached to the photosensitive member 201. Such a toner may contaminate the rear surface of the recording paper. A cleaner 204 removes such a waste toner.
This cleaner 204 includes a first metal cleaner roller 205 and a second metal cleaner roller 206 that is provided downstream from the first cleaner roller 205 in the rotation direction of the transfer belt 202. A voltage of xe2x88x92600V is applied to the first cleaner roller 205, and a voltage of +1000V is applied to the second cleaner roller 206. Then, the first cleaner roller 205 enhances the negative charge of the waste toner remaining on the transfer belt 202, and the second cleaner roller 206 removes the negatively charged waste toner remaining on the transfer belt 202. Moreover, the toner attached to the first and second cleaner rollers 206 and 206 is scraped off by a cleaning blade 207.
Furthermore, JP 7-319356 A discloses a configuration in which a metal roller and an elastic roller are combined. As shown in FIG. 13, this configuration uses a first cleaner roller 221 that is a metal roller arranged facing the photosensitive member 220 via a small gap and a second cleaner roller 222 that is pressed onto the photosensitive member 220 downstream from the first cleaner roller 221 in the rotation direction of the photosensitive member 220. The voltage having a polarity opposite to the charging polarity of the toner is applied to the first cleaner roller 221, whereby the waste toner on the photosensitive member 220 is adsorbed by the first cleaner roller 221. The second cleaner roller 222 removes the attached substances other than waste toner on the photosensitive member 220 by the force of the electric field and the mechanical shear force. The first and second cleaner rollers 221 and 222 are provided with a blade 224 for scraping off toner or attached substances on the surface of the cleaner rollers 221 and 222.
Furthermore, JP 9-90840 A discloses a configuration using a fur brush roller as a cleaner roller.
Furthermore, as a cleaning device for removing off waste toner on an intermediate transfer belt and a transfer belt, one having a configuration in which a rubber cleaning blade is pressed onto the surface of the belt so as to scrape off the waste toner is well known.
However, the above-mentioned conventional image forming apparatus disclosed in JP 9-80934 A, etc. has the following problems. First, in order to equalize the charge of the toner, a power source for high voltage is required. Furthermore, the surface of the transfer belt is chemically deteriorated since toner on the transfer belt is charged by minute discharge. Furthermore, since the voltage is applied to the charging member, a large amount of toner having an opposite polarity is attached onto the charging member, thus disturbing the charging by the minute discharge.
In the cleaning device, it is required to improve the cleaning performance for completely removing waste toner on the surface of the transfer belt or the intermediate transfer belt. In the conventional configuration using a metal roller shown in FIG. 12, the second cleaner roller 206 provided at the downstream in the rotation direction of the transfer belt 202 so as to be pressed onto the transfer belt 202, as well as the first cleaner roller 205 provided at the upper stream in the rotation direction of the transfer belt 202, provides the waste toner remained on the transfer belt 202 with opposite charges. Therefore, the waste toner remaining on the transfer belt 202 has the same polarity as that of the second cleaner roller 206, which makes it difficult to remove the waste toner remaining on the transfer belt 202 by the use of the second cleaner roller 206.
Furthermore, in the conventional configuration shown in FIG. 13, since the first cleaner roller 221 is arranged facing the photosensitive member 220 via a gap, it is not possible to remove sufficiently the waste toner on the photosensitive member 220. On the other hand, in the second cleaner roller 222, which is an elastic roller, provided downstream in the rotation direction of the photosensitive member 220 so as to be pressed onto the photosensitive member 220, the abrasion resistance is lower as compared with a metal roller, and the lifetime is short. Moreover, high accuracy cannot be secured, variation in the resistance due to the adsorbed moisture is large and furthermore the cost is high.
The conventional configuration in which a fur brush roller is used as a cleaner roller has the following problems: for example, the performance of removing toner is deteriorated because the fur lies flat after a long time of use; the resistance value is varied due to the absorbed moisture; the fur brush is clogged with toner; toner scatters by being blown away by the brush; toner is attached again onto the belt from the fur brush; and the like. Furthermore, a power source for a high voltage is required, and a fur brush itself is expensive, thus raising the cost as a whole.
Furthermore, in the configuration using a rubber cleaning blade, since the pressing power at the tip of the blade is large, the cleaning blade may damage the surface of the belt, and the cleaning blade may be deteriorated by abrasion. Furthermore, the load torque is increased by the friction force on a portion where the cleaning blade is in contact with and pressed onto the surface of the belt. When the cleaning blade is separated, toner accumulated at the tip of the blade scatters. When the cleaner unit is replaced with a new one, at the same time the tip of the blade is separated from the belt, the toner attached to the tip of the blade may drop off, and contaminate the inside and periphery of the apparatus.
It is an object of the present invention to provide an image forming apparatus capable of reliably removing waste toner on a toner supporting member of a transfer belt, and the like, with a simple configuration and to provide a transfer belt unit, a cleaning device and a cleaner unit, which are used for the image forming apparatus.
In order to attain the above-mentioned object, a first configuration of an image forming apparatus according to the present invention includes a toner supporting member that moves with charged toner supported on the surface thereof, a cleaner member that is rotated while being pressed onto the toner supporting member, a potential supplying means for supplying a potential for electrically attracting the toner from the toner supporting member to the cleaner member, and a frictionally charging member that is pressed onto the toner supporting member upstream from the cleaner member in the moving direction on the toner supporting member. According to the first configuration of the image forming apparatus, the toner remaining on the toner supporting member can be charged by friction with a normal polarity until the toner reaches the position of the cleaner member. Therefore, the waste toner on the toner supporting member can be cleaned off reliably by the cleaner member.
Furthermore, it is preferable in the configuration of the image forming apparatus according to the present invention that the toner supporting member is an intermediate transfer belt, and that there is provided a toner image forming means for forming a toner image charged with a predetermined polarity on the intermediate transfer belt, and a transfer means for transferring the toner image from the intermediate transfer belt onto a recording paper, wherein the cleaner member is pressed onto the intermediate transfer belt between the transfer means and the toner image forming means, and the frictionally charging member is positioned between the transfer means and the cleaner member. With such a preferred configuration, since the frictionally charging member is positioned between the transfer means and cleaner member, the toner remaining after transfer can be brought into contact with the frictionally charging member. Therefore, it is possible to remove positive charges from the toner at the same time, the toner can be charged negatively. The positive charges had been given at the time of transfer to the toner originally having negative polarity. Thus, toner carried to the cleaner portion assumes the normal polarity. As a result, it is possible to remove the remaining toner by a cleaner member to which positive voltage is applied. Furthermore, by employing such a configuration, the waste toner can be removed with a much lower cleaning voltage. Lowering the cleaning voltage makes it possible to suppress the load variation due to the cleaner member, thus suppressing the displacement of the cleaner member when the cleaner member is separated. Furthermore, in this case, it is preferable that the frictionally charging member is a rotatable roller, and the transfer means is a transfer roller to which a voltage is applied while switching between a voltage with a polarity opposite to the charging polarity of the toner and a voltage with a polarity the same as the charging polarity of the toner. The voltage having the same polarity as the charging polarity of the toner is applied to the transfer roller, then the voltage having a polarity opposite to the charging polarity of the toner while allowing the frictionally charging member to be rotated at least once. In order to clean off the transfer roller, an opposite voltage is applied to the transfer roller. At this time, a large amount of toners on the intermediate transfer belt are attached to the frictionally charging member, thereby making it impossible to be in contact with toner on the intermediate transfer belt. In this case, when the voltage having the same polarity as the charging polarity of the toner is applied to the transfer roller, then the voltage having the opposite polarity to the charging polarity of the toner, and in this state, the frictionally charging member is allowed to be rotated at least once, the toners attached to the frictionally charging member are attached to the intermediate transfer belt. Therefore, the frictionally charging member can be in contact with the toner on the intermediate transfer belt again.
Furthermore, it is preferable in the first configuration of the image forming apparatus according to the present invention that the toner supporting member is a transfer belt for conveying a recording paper and that there are provided a toner image forming means for forming a toner image charged with a predetermined polarity on the recording paper, a peeling means for peeling the recording paper from the transfer belt, wherein the cleaner member is pressed onto the transfer belt between the peeling means and the toner image forming means, and the frictionally charging member is positioned between the peeling means and the cleaner member. With such a preferred configuration, since the frictionally charging member is positioned between the peeling means and the cleaner member, the toner remaining after transfer can be brought into contact with the frictionally charging member. Therefore, it is possible to remove positive charges from the toner at the same time, the toner can be charged negatively. The positive charges are given at the time of transfer to the toner originally having negative polarity. Thus, toner carried to the cleaner portion comes to have the normal polarity. As a result, it is possible to remove the remaining toner by a cleaner member to which positive voltage is applied. Furthermore, by employing such a configuration, the waste toner can be removed with a much lower cleaning voltage. Lowering the cleaning voltage makes it possible to suppress the load variation due to the cleaner member, thus suppressing the displacement of the cleaner member when the cleaner member is separated.
Furthermore, it is preferable in the first configuration of the image forming apparatus according to the present invention that the frictionally charging member is electrically grounded. With such a preferred configuration, since toner is not attached excessively to the frictionally charging member, a stable transfer of charges can be performed because the frictionally charging member can be in contact with toner on the toner supporting member. Furthermore, since no minute discharge occurs between the frictionally charging member and toner supporting member, the surface of the toner supporting member is not deteriorated. Furthermore, even if the semiconductive belt is used as the toner supporting member, it does not affect the conditions of secondary transfer or primary transfer. Furthermore, it is possible to break the wraparound of electric current from the cleaner member and thus to prevent the cleaner member from affecting the process conditions of other members.
Furthermore, it is preferable in the first configuration of the image forming apparatus according to the present invention that the surface of the frictionally charging member has a charging polarity opposite to that of the toner. With such a preferred configuration, when the frictionally charging member is in contact with toner, a larger amount of positive charges on the surface of toner can be removed by only one touch, and therefore waste toner on the toner supporting member can be removed completely.
Furthermore, it is preferable in the first configuration of the image forming apparatus according to the present invention that the frictionally charging member is a rotatable roller that is in contact only with the toner supporting member, and the frictionally charging member and the toner supporting member move at different speeds from each other at the contact portion therebetween. With such a preferred configuration, toner on the toner supporting member can be provided with both electric attraction force and mechanical shear force. Therefore, the waste toner on the toner supporting member can be removed completely. Furthermore, since there is not provided members for scraping off the toner on the surface of the frictionally charging member, it is possible to simplify the configuration around the frictionally charging member.
Furthermore, it is preferable in the first configuration of the image forming apparatus according to the present invention that the frictionally charging member is a rotatable roller that is in contact only with the toner supporting member, and the frictionally charging member and the toner supporting member move in the same direction at the contact portion therebetween. With such a preferred configuration, the toner attached to the frictionally charging member is allowed to pass through the nip portion between the toner supporting member and the frictionally charging member. Therefore, since the opportunity that the frictionally charging member is brought into contact with toner, it is possible to remove a larger amount of positive charges on the surface of the toner by the frictionally charging member. As a result, the waste toner on the toner supporting member can be removed completely.
Furthermore, it is preferable in the first configuration of the image forming apparatus according to the present invention that the frictionally charging member is separable from the toner supporting member, and a driving force is transmitted from a driving portion of the toner supporting member to the frictionally charging member. With such a preferred configuration, even when the frictionally charging member is separated, the driving force can be transmitted stably from the driving portion of the toner supporting member to the frictionally charging member.
Furthermore, it is preferable in the first configuration of the image forming apparatus according to the present invention that an opposing electrode is provided at a position facing the frictionally charging member while sandwiching the toner supporting member between the opposing electrode and the frictionally charging member. With such a preferred configuration, it is possible to increase the contact pressure between the frictionally charging member and the toner on the toner supporting member. Therefore, it is possible to smoothen an unevenness of the toner layer so that a larger amount of toner can be brought into contact with the frictionally charging member. At the same time, it is possible to increase the true area of contact when the frictionally charging member is brought into contact with the toner. As a result, there is an increased opportunity that the frictionally charging member is in contact with toner, whereby a larger amount of positive charges can be removed from the surface of the toner by only one touch. Therefore, it is possible to remove the waste toner on the toner supporting member by the cleaner member. Furthermore, in this case, it is preferable that the frictionally charging member is electrically grounded, and the opposing electrode and the cleaner member have the same potential. With such a preferred configuration, an electric field is generated on the portion in which the frictionally charging member is in contact with the toner on the toner supporting member. This electric field allows positive charges to move in the direction toward the frictionally charging, and negative charges to move in the direction toward the toner. Therefore, when the frictionally charging member is in contact with toner, it is possible to remove a larger amount of positive charges on the toner by only one touch. At the same time, the toner can be changed negatively. Moreover, since a plurality of members are made to have the same potential, it is not necessary to provide an additional electric power source or terminal, thus realizing a simple and low-price configuration of the apparatus. Furthermore in this case, it is preferable that the opposing electrode is made of a conductive brush. With such a preferred configuration, a cleaning electric field can be formed stably over the entire region of the cleaning nip. Since the cleaning field can be formed stably, it is possible to improve the performance of cleaning off toner on the intermediate transfer belt. As a result, even if the cleaning voltage is set low, it is possible to remove the waste toner completely and stably. Furthermore, by using the opposing electrode, it is possible to press the toner supporting member onto the cleaner member over the entire region of the cleaning nip. Therefore, even if there is a distortion or deformation in the toner supporting member, it is possible to secure the stable cleaning nip. Consequently, it is possible to secure both the friction force and electric field force, which are applied to the toner on the toner supporting member. Thus, the sufficient cleaning performance can be exhibited, and the waste toner can be removed stably and completely.
Furthermore, it is preferable in the first configuration of the image forming apparatus according to the present invention that the frictionally charging member is a rotatable roller having a surface roughness Ra of 5-20 xcexcm. With such a preferred configuration, since the mechanical shear force applied to the toner on the toner supporting member is increased, aggregated toner can be pulverized. Therefore, it is possible to prevent the aggregated toner from deforming the toner supporting member. Therefore, it is possible to bring the toner in the vicinity of the aggregated toner into contact with the frictionally charging member and the cleaner member. Thus, the toner can be removed more completely. Furthermore, in this case, it is preferable that the surface of the frictionally charging member is subjected to a sand-blasting procedure.
Furthermore, it is preferable in the image forming apparatus of the first configuration according to the present invention that the cleaner member is an aluminum roller having an alumite layer on the surface thereof, comprising a scraper for removing the toner while being pressed onto the surface of the cleaner member.
Furthermore, a first configuration of a transfer belt unit according to the present invention includes as an integrated unit; a high resistance intermediate transfer belt which is supported rotatably, and on which toner charged with a predetermined polarity is transferred to a toner image by primary transfer, and further the toner image is transferred onto a recording paper by secondary transfer; a cleaner roller which is pressed onto the intermediate transfer belt downstream from the secondary transfer position in the rotation direction of the intermediate transfer belt and to which a voltage with a polarity opposite to the predetermined polarity of the toner is applied; a frictionally charging member that is pressed onto the intermediate transfer belt between the secondary transfer position and the cleaner roller, wherein the integrated unit is attached to a main body of the image forming apparatus detachably. According to the first configuration of the transfer belt unit, when the transfer belt unit is replaced with new one, it is possible to eject the waste toner to the outside of the apparatus without spilling of toner at the time of the replacement of the intermediate transfer belt. Therefore, by integrating the members into one unit, maintenance can be performed easily without contaminating the inside of the image forming apparatus main body with the waste toner. Furthermore, integrated configuration makes it possible to maintain the accuracy of the positional relationship between the intermediate transfer belt and the cleaner roller to the predetermined value easily. Therefore, it is possible to keep the image forming apparatus main body in good condition for a long time with only simple maintenance.
Furthermore, it is preferable in the first configuration of the transfer belt unit according to the present invention that the frictionally charging member is electrically grounded.
Furthermore, it is preferable in the first configuration of the transfer belt unit according to the present invention that the surface of the frictionally charging member has a charging polarity opposite to the charging polarity of the toner.
Furthermore, it is preferable in the first configuration of the transfer belt unit according to the present invention that the frictionally charging member is a rotatable roller that is in contact only with the toner supporting member, and the frictionally charging member and the toner supporting member move at different speeds from each other at the contact portion therebetween.
Furthermore, it is preferable in the first configuration of the transfer belt unit according to the present invention that the frictionally charging member is a rotatable roller that is in contact only with the toner supporting member, and the frictionally charging member and the toner supporting member move in the same direction at the contact portion therebetween.
Furthermore, it is preferable that the first configuration of the transfer belt unit according to the present invention includes a driving axis for rotating the intermediate transfer belt suspended therefrom, a disjunction means for separating the frictionally charging member from the intermediate transfer belt, and a driving force transmitting means for transmitting a driving force from the driving axis to the frictionally charging member.
Furthermore, it is preferable in the first configuration of the transfer belt unit according to the present invention that an opposing electrode is provided at a position facing the frictionally charging member while sandwiching the intermediate transfer belt between the opposing electrode and the frictionally charging member. Furthermore, in this case, it is preferable that the opposing electrode and the cleaner roller have the same potential.
Furthermore, it is preferable in the first configuration of the transfer belt unit according to the present invention that the frictionally charging member is a rotatable roller, having a surface roughness Ra of 5-20 xcexcm. Furthermore, in this case, it is preferable that the surface of the frictionally charging member is subjected to a sand-blasting procedure.
Furthermore, it is preferable in the first configuration of the transfer belt unit according to the present invention that the cleaner roller is an aluminum roller, having an alumite layer on the surface thereof, and that there is provided a scraper for removing the toner while being pressed onto the surface of the cleaner roller.
Furthermore, a second configuration of an image forming apparatus according to the present invention includes a toner supporting member that moves with charged toner supported on the surface thereof, a cleaner member that is rotated while being pressed onto the toner supporting member, and a potential supplying means for supplying potential for electrically attracting the toner from the toner supporting member to the cleaner member, wherein the cleaner member is made of metal and has a high-resistance layer on the surface thereof. According to the second configuration of the image forming apparatus, no charges are accumulated on the surface of the cleaner member. Moreover, charges opposite to the charging polarity of the toner are not provided onto the cleaner member. Furthermore, the surface of the cleaner member has an excellent abrasion resistance property and the shape is not changed. Furthermore, as compared with the configuration in which the fur brush is used, a cleaner member is low-price and can be formed in a simple configuration. Therefore, it is possible to obtain a high quality image stably for a long time with a simple configuration.
Furthermore, it is preferable in the second configuration of the image forming apparatus according to the present invention that the toner supporting member is an intermediate transfer belt and that there are provided a toner image forming means for forming a toner image charged with a predetermined polarity on the intermediate transfer belt, and a transfer means for transferring the toner image from the intermediate transfer belt onto a recording paper, wherein the cleaner member is pressed onto the intermediate transfer belt between the transfer means and the toner image forming means. Furthermore, in this case, it is preferable that a first opposing electrode is provided at a position facing the cleaner member while sandwiching the intermediate transfer belt between the first opposing electrode and the cleaner member. With such a preferred configuration, over the entire region of the cleaning nip of the cleaner member, it is possible to form the stable cleaning electric field for attracting the toner toward the cleaner member. Furthermore, in this case, it is preferable that the image forming apparatus includes a conductive pretreatment member which is electrically grounded and is pressed onto the intermediate transfer belt between the transfer means and the cleaner member. With such a preferred configuration, it is possible to remove the opposite charge given to toner at the time of secondary transfer and at the same time, the toner can be charged normally. As a result, it is possible to remove the toner remaining after the secondary transfer with a cleaner member at lower voltage. Furthermore, in this case, it is preferable that the pretreatment member is a rotatable roller that is in contact only with the intermediate transfer belt, and the pretreatment member and the intermediate transfer belt move at different speeds from each other at the contact portion therebetween. With such a preferred configuration, since toner can roll at the portion in which the pretreatment member is in the contact with the intermediate transfer belt, the contact opportunity between the pretreatment member and toner is increased. As a result, a larger amount of the opposite charges on the surface of the toner can be removed in advance. In this case, it is furthermore preferable that the pretreatment member is a rotatable roller that is in contact only with the intermediate transfer belt, and the pretreatment member and the intermediate transfer belt move in the same direction at the contact portion therebetween. With such a preferred configuration, since toner can roll at the portion in which the pretreatment member is in contact with the intermediate transfer belt, the contact opportunity between the pretreatment member and toner is increased. As a result, a large amount of opposite charges on the surface of the toner can be removed by the pretreatment member. In this case, since a member for scraping off the toner on the surface of the pretreatment member is not provided, the configuration around the pretreatment member can be simplified. In this case, it is further preferable that a second opposing electrode is provided at a position facing the pretreatment member while sandwiching the intermediate transfer belt between the second opposing electrode and the pretreatment member. With such a preferred configuration, since the contact opportunity in which the pretreatment member is in contact with the toner is increased, it is possible to remove the waste toner completely by the cleaner member. Furthermore, in this case, it is preferable that the second opposing electrode and the cleaner member have the same potential. With such a preferred configuration, an electric field is generated on the portion in which the pretreatment member is in contact with the toner on the intermediate transfer belt, it is possible to remove a larger amount of opposite charges on the surface of the toner by only one touch, and at the same time, the toner can be charged normally. Moreover, since a plurality of members are made to have the same potential, it is not necessary to provide an additional electric power source or terminal, thus realizing the apparatus configuration simply and at low cost. Furthermore, in this case, it is preferable that the cleaner member is separable from the intermediate transfer belt. With such a preferred configuration, since a toner image is not disturbed due to the cleaner member, it is possible to overlap toner images by rotating the intermediate transfer belt several times. Thus, it is possible to provide a whole apparatus having a small size at low cost. In this case, it is further preferable that a first conductive brush that is electrically grounded is provided at a position facing the cleaner member while sandwiching the intermediate transfer belt between the first conductive brush and the cleaner member. With such a preferred configuration, load variation when the cleaner member is separated can be suppressed. As a result, a high quality image can be obtained by suppressing the displacement of each toner image. Furthermore, in this case, it is preferable that the image forming apparatus includes a pretreatment roller that is electrically grounded and is pressed onto the intermediate transfer belt between the transfer means and the cleaner member, and a pretreatment roller disjunction mechanism for separating the pretreatment roller from the intermediate transfer belt. Furthermore, it is preferable that a second conductive brush having the same potential as that of the cleaner member is provided at a position facing the pretreatment roller while sandwiching the intermediate transfer belt between the second conductive brush and the pretreatment roller. In this case, it is preferable that an absolute value of the voltage applied to the cleaner member is 150-400V.
Furthermore, it is preferable in the second configuration of an image forming apparatus according to the present invention that the toner supporting member is a transfer belt for conveying a recording paper, and that there are provided a toner image forming means for forming a toner image charged with a predetermined polarity on the recording paper, and a peeling means for peeling the recording paper from the transfer belt, wherein the cleaner member is pressed onto the transfer belt between the peeling means and the toner image forming means. Furthermore, in this case, it is preferable that a first opposing electrode is provided at a position facing the cleaner member while sandwiching the intermediate transfer belt between the first opposing electrode and the cleaner member. Furthermore, in this case, it is preferable that the image forming apparatus includes a conductive pretreatment member that is electrically grounded and is pressed onto the intermediate transfer belt between the peeling means and the cleaner member. Furthermore, in this case, it is preferable that a second opposing electrode is provided at a position facing the pretreatment member while sandwiching the transfer belt between the second opposing electrode and the pretreatment member. Furthermore, in this case, it is preferable that the second opposing electrode and the cleaner member have the same potential.
Furthermore, it is preferable in the second configuration of an image forming apparatus according to the present invention that the toner supporting member has a surface resistivity of 1xc3x97108 xcexa9/xe2x96xa1 or more and 1xc3x971010 xcexa9/xe2x96xa1 or less, and a volume resistivity of 1xc3x97108 xcexa9xc2x7cm or more and 1xc3x971010 xcexa9xc2x7cm or less.
Furthermore, it is preferable in the second configuration of an image forming apparatus according to the present invention that the cleaner member has an anodic oxidation coating on the surface thereof. Furthermore, in this case, it is preferable that the cleaner member is made of aluminum, having an alumite layer on the surface thereof.
Furthermore, it is preferable that the second configuration of an image forming apparatus according to the present invention includes a scraper for scraping off the toner by being pressed onto the surface of the cleaner member. With such a preferred configuration, it is possible to obtain a high quality image for a long time with an apparatus of simple configuration at low price. Furthermore, in this case, it is preferable that the scraper is a thin metal plate having a thickness of 30-80 xcexcm. Furthermore, in this case, it is preferable that a lubricant is attached to the surface of the cleaner member. With such a preferred configuration, since the frictional coefficient between the cleaner member and the scraper is reduced. The abrasion of the scraper can be reduced. Furthermore, since the force of the cleaner member to carry toners is reduced, the toner can be scraped off easily by the scraper. As a result, it is possible to obtain a high quality image stably for a long time. Furthermore, in this case, it is preferable that the surface roughness Rmax of the cleaner member is 0.5-8 xcexcm.
Furthermore, it is preferable in the second configuration of the image forming apparatus according to the present invention that the cleaner member and the toner supporting member move at different speeds from each other at a contact portion therebetween. With such a preferred configuration, the toner on the toner supporting member can be provided with both an electric attraction force and mechanical shear force simultaneously. Therefore, the waste toner on the toner supporting member can be removed completely. As a result, it is possible to obtain a high quality image stably.
Furthermore, it is preferable in the second configuration of the image forming apparatus according to the present invention that the cleaner member and the toner supporting member move in opposite directions at a contact portion therebetween. With such a preferred configuration, toner on the toner supporting member can be provided with a mechanical shear force without increasing the peripheral speed. As a result, it is possible to increase the lifetime of the cleaner member and at the same time to suppress the energy consumption by the rotation of the cleaner member.
Furthermore, a second configuration of a transfer belt unit according to the present invention includes an intermediate transfer belt that is supported rotatably, and on which toner charged with a predetermined polarity is transferred to a toner image by primary transfer, and further the toner image is transferred onto a recording paper by secondary transfer; a cleaner roller made of metal and having a high resistance layer on the surface thereof, which is rotated while being pressed onto the intermediate transfer belt downstream from the secondary transfer position in the rotation direction of the intermediate transfer belt; a potential supplying means for supplying a potential for electrically attracting the toner to the cleaner roller; and a scraper for scraping off the toner while being pressed onto the surface of the cleaner roller; wherein the integrated unit is attached to a main body of the image forming apparatus detachably. According to the second configuration of the transfer belt unit, when the transfer belt unit is replaced with a new one, when the intermediate transfer belt is replaced with a new one, the waste toner can be ejected without spilling toner. Therefore, maintenance can be performed easily without contaminating the inside of the image forming apparatus main body with the waste toner. Furthermore, since the intermediate transfer belt, the cleaner roller and scraper are integrated into one unit, it is possible to maintain the accuracy of positional relationship between such integrated members and the whole apparatus. Therefore, it is possible to keep the apparatus main body in good condition for a long time with only simple maintenance. Moreover, charges are not accumulated on the surface of the cleaner roller, and furthermore, the toner is not provided with charges of the opposite polarity to the charging polarity. Furthermore, the surface of the cleaner roller has an excellent abrasion resistance property and the shape of the roller is not changed. Furthermore, as compared with the configuration in which the fur brush is used, the cleaner roller is inexpensive and the configuration is simple. As a result, with such a configuration, cleaning can be performed for a long time stably. Furthermore, the lifetime of the transfer belt unit is increased, and thus the frequency of the maintenance is reduced. Consequently, the cost per paper can be reduced and at the same time, the apparatus can be used more easily. Furthermore, in this case, it is preferable that the intermediate transfer belt has a surface resistivity of 1xc3x97108 xcexa9/xe2x96xa1 or more and 1xc3x971010 xcexa9/xe2x96xa1 or less, and a volume resistivity of 1xc3x97108 xcexa9xc2x7cm or more and 1xc3x971010 xcexa9xc2x7cm or less. Furthermore, in this case, it is preferable that the cleaner roller has an anodic oxidation coating on the surface thereof. With such a preferred configuration, on the surface of the cleaner roller, a layer having a high hardness and high electric resistance can be formed easily. As a result, the increased lifetime of the transfer belt unit and low-price configuration of the transfer belt unit can be realized. Furthermore, in this case, it is preferable that the cleaner roller is made of aluminum, having an alumite layer on the surface thereof. Furthermore, in this case, it is preferable that the scraper is a thin metal plate having a thickness of 30-80 xcexcm. With such a preferred embodiment, the abrasion resistance of the scraper can be enhanced, and the lifetime of the transfer belt unit can be increased. Furthermore, in this case, it is preferable that a lubricant is attached to the surface of the cleaner roller. With such a preferred embodiment, it is possible to scrape off the toner with the scraper for a long time. Consequently, the long lifetime of the transfer belt unit can be attained. Furthermore, in this case, it is preferable that the surface roughness Rmax of the cleaner roller is 0.5-8 xcexcm. Furthermore, in this case, it is preferable that the cleaner roller and the intermediate transfer belt move at different speeds from each other at a contact portion therebetween. With such a preferred configuration, the toner on the intermediate transfer belt can be provided with both an electric attraction force and a mechanical shear force. Therefore, the waste toner on the intermediate transfer belt can be removed completely. Furthermore, in this case, it is preferable that the cleaner roller and the intermediate transfer belt move in the opposite direction at a contact portion therebetween. With such a preferred configuration, the toner on the intermediate transfer belt can be provided with mechanical shear force without increasing the peripheral speed. As a result, the speed in which the scraper and cleaner roller are in contact and scrape with each other is reduced, and thus it is possible to scrape off the toner stably with the scraper for a long time. Therefore, the lifetime of the transfer belt unit can be increased.
Furthermore, in this case, it is preferable that a first opposing electrode is provided at a portion facing the cleaner roller while sandwiching the intermediate transfer belt between the first opposing electrode and the cleaner roller. With such a preferred configuration, a cleaning electric field for attracting toner toward the cleaner roller can be formed stably over the entire region of the cleaning nip. Furthermore, in this case, it is preferable that there is provided a conductive pretreatment member that is electrically grounded and is pressed onto the intermediate transfer belt between the second transfer position and the cleaner roller. With such a preferred configuration, it is possible to remove an opposite charge given from the toner at the time of secondary transfer, and at the same time, the toner can be charged normally. As a result, it is possible to remove the toner remaining after the second transfer by the cleaner member of lower voltage. Furthermore, in this case, it is preferable that the pretreatment member is a rotatable roller that is in contact only with the intermediate transfer belt, and the pretreatment member and the intermediate transfer belt move at different speeds from each other at the contact portion therebetween. With such a preferred configuration, since toner can roll on the portion in which the pretreatment member is in contact with the intermediate transfer belt, the contact opportunity between the pretreatment member and toner is increased. As a result, a larger amount of opposite charges on the surface of toner can be removed in advance. Furthermore, in this case, it is preferable that the pretreatment member is a rotatable roller that is in contact only with the intermediate transfer belt, and the pretreatment member and the intermediate transfer belt move in the same direction at the contact portion therebetween. With such a preferred configuration, the toner attached to the pretreatment member is allowed to pass through the nip to the intermediate transfer belt. Therefore, since the opportunity that the pretreatment member is brought into contact with the toner increases, it is possible to remove a larger amount of positive charges on the surface of the toner by the pretreatment member. In this case, a member for scraping off the toner on the surface of the pretreatment member is not provided, it is possible to simplify the configuration around the pretreatment member. In this case, it is further preferable that a second opposing electrode is provided at a position facing the pretreatment member while sandwiching the intermediate transfer belt between the second opposing electrode and the pretreatment member. With such a preferred configuration, it is possible to increase the contact pressure between the pretreatment member and toner. Consequently, since the contact opportunity between the pretreatment member and toner is increased, the waste toner on the intermediate transfer belt can be removed completely by the cleaner roller. Furthermore, in this case, it is preferable that the second opposing electrode and the cleaner roller have the same potential. With such a preferred configuration, since an electric field is generated on the portion in which the pretreatment member is in contact with toner on the intermediate transfer belt, when the pretreatment member is in contact with toner, it is possible to remove a larger amount of positive charges on the toner at one touch and at the same time, and the toner can be charged normally. Furthermore, because the second opposing electrode and the cleaner roller have the same potential, it is not necessary to provide an additional power source or terminal. As a result, it is possible to realize the simple and inexpensive configuration. Furthermore, in this case, it is preferable that the cleaner roller is separable from the intermediate transfer belt. With such a preferred configuration, since the toner image is not disturbed due to the cleaner roller, it is possible to overlap toner images by rotating the intermediate transfer belt several times. Furthermore, in this case, it is preferable that a first conductive brush that is electrically grounded is provided at a position facing the cleaner roller while sandwiching the intermediate transfer belt between the first conductive brush and the cleaner roller. With such a preferred configuration, a cleaning electric field can be formed stably over the entire region of the cleaning nip, and the cleaning performance of the toner on the intermediate transfer belt is improved. As a result, even if the cleaning voltage is set to be low, it is possible to remove the waste toner completely and stably. Furthermore, it is possible to suppress the load variation when the cleaner roller is separated. Consequently, a high quality image can be obtained by suppressing the displacement of each toner image. Furthermore, in this case, it is preferable that the image forming apparatus includes a pretreatment roller that is electrically grounded and is pressed onto the intermediate transfer belt between the secondary transfer position and the cleaner roller, and a pretreatment roller disjunction mechanism for separating the pretreatment roller from the intermediate transfer belt. With such a preferred configuration, since a toner image is not disturbed due to the cleaner member, it is preferable to overlap toner images by rotating the intermediate transfer belt several times. Furthermore, in this case, it is possible that a second conductive brush having the same potential as that of the cleaner roller is provided at a position facing the pretreatment roller while sandwiching the intermediate transfer belt between the second conductive brush and the pretreatment roller. With such a preferred configuration, an electric field can be formed stably over the entire region of the nip of the pretreatment portion. Thus, the performance of charging toner on the intermediate transfer belt can be improved. Furthermore, since it is possible to suppress the load variation when the pretreatment roller is separated, a high quality image can be obtained while suppressing the displacement of each toner image.
Furthermore, a configuration of the cleaning device according to the present invention includes a cleaner member, which is rotated while being pressed onto a toner supporting member that moves with charged toner supported on the surface thereof and which maintains the potential for electrically attracting the toner from the toner supporting member, wherein the cleaner member is made of a metal having a high resistance layer on the surface thereof. According to the configuration of the cleaning device, electric charges are not accumulated on the surface of the cleaner member, and the toner is not provided with charges opposite to the charging polarity. Furthermore, since the cleaner member is made of a metal having a high electric resistance layer on the surface thereof, the surface of the cleaner member has an excellent abrasion resistance and the shape is not changed. Furthermore, as compared with the configuration in which the fur brush is used, the cleaner member is inexpensive and the configuration is simple. As a result, it is possible to perform a cleaning operation stably for a long time with a simple configuration.
Furthermore, it is preferable in the cleaning device according to the present invention that the cleaner member has an anodic oxidation coating on the surface thereof. With such a preferred configuration, a layer that is inexpensive and has high hardness and high electric resistance can be formed on the surface of the cleaner member easily. Consequently, the lifetime of the transfer belt unit can be increased and the configuration of the transfer belt unit can be inexpensive. Furthermore, in this case, it is preferable that the cleaner member is made of aluminum, having an alumite layer on the surface thereof.
Furthermore, it is preferable in the configuration of the cleaning device according to the present invention that the cleaner member and the toner supporting member move at different speeds from each other at a contact portion therebetween. With such a preferred configuration, the toner on the toner supporting member can be provided with both electric attraction force and mechanical shear force. Therefore, the waste toner on the toner supporting member can be removed completely.
Furthermore, it is preferable in the configuration of the cleaning device according to the present invention that the cleaner member and the toner supporting member move in the opposite direction at a contact portion therebetween. With such a preferred configuration, the toner on the toner supporting member can be provided with mechanical shear force without increasing the peripheral speed.
Furthermore, it is preferable in the configuration of the cleaning device according to the present invention that there is provided a scraper for scraping off the toner by being pressed onto the cleaner member. With such a preferred configuration, the toner on the cleaner member can be removed with an inexpensive and simple configuration. Furthermore, in this case, it is preferable that the scraper is a thin metal plate having a thickness of 30-80 xcexcm. With such a preferred configuration, since the abrasion resistance of the scraper can be enhanced, it is possible to prevent the defective scraping of toner due to the faults or gaps at the tip of the scraper. Therefore, it is possible to remove toner on the cleaner roller for a long time stably and completely. Furthermore, in this case, it is preferable that a lubricant is attached to the surface of the cleaner member. With such a preferred configuration, the frictional coefficient between the cleaner member and the scraper is reduced, and the abrasion of the scraper can be reduced. Furthermore, since the force of the cleaner member to carry the toner is reduced, the toner on the cleaner member can be scraped off easily. As a result, it is possible to scrape off the toner with the scraper for a long time. Furthermore, in this case, it is preferable that the surface roughness Rmax of the cleaner member is 0.5-8 xcexcm. With such a preferred configuration, it is possible to scrape off the toner on the cleaner member with the scraper.
Furthermore, a configuration of the cleaner unit according to the present invention includes, as an integrated unit, a cleaner member made of metal, a high resistance layer on the surface thereof, which is rotated while being pressed onto a toner supporting member that moves with charged toner supported on the surface thereof; a potential supplying means for supplying potential for electrically attracting the toner to the cleaner member, a scraper for scraping off the toner by being pressed onto the cleaner member, a waste toner case for collecting the toner scraped off from the cleaner member; and a seal member for preventing the toner from leaking from the gap between the cleaner member, and the scraper and the waste toner case; wherein the integrated unit is attached to the toner supporting member detachably. According to the configuration of this cleaner unit, the inside of the waste toner case is sealed with a sealing member and cleaner member, and the waste toner is not scattered to the outside of the apparatus when the cleaner unit is replaced with a new one. Furthermore, since the waste toner can be disposed of to the outside of the apparatus by the replacement of the attachable and detachable cleaner unit, it is possible to keep the apparatus main body in good condition for a long time by simple maintenance. Furthermore, since the cleaner member, the scraper, and the seal member are integrated into one unit, the positional accuracy of the whole apparatus can be maintained simply to the predetermined value. Furthermore, electric charges are not accumulated on the surface of the cleaner member, and toner is not provided with charges opposite to the charging polarity. Furthermore, the surface of the cleaner member has an excellent abrasion resistance and the shape is not changed. Furthermore, as compared with the configuration in which the fur brush is used, the cleaner member is inexpensive and the configuration is simple. As a result, it is possible to perform cleaning operation stably for a long time with an inexpensive configuration.
Furthermore, it is preferable in the cleaner unit according to the present invention that the cleaner member is made of aluminum, having an alumite layer on the surface thereof. With such a preferred configuration, a layer that is inexpensive and has high hardness and high electric resistance can be formed on the surface of the cleaner member easily.
Furthermore, it is preferable in the cleaner unit according to the present invention that the surface roughness Rmax of the cleaner member is 0.5-8 xcexcm. With such a preferred configuration, the toner on the cleaner member can be scraped off with the scraper.